Why are these red dots appearing in my viewport?
The red dots are appearing because of Subsurface Scattering (SSS), or translucency. When you turn on SSS in Cycles, there will be strange colored dots unless you render at a higher sample count. Some possible ways to solve your problem are


Reduce the amount of SSS by adjusting the Subsurface slider.
Adjust the Subsurface Raduis


Because doughnuts are usually made of bread, you should have SSS values close to 0.05, and SSS Radius values close to (0.1, 0.1, 0.1)